Table of contents

Table of contents

FOREWORD

“Diagnosis” means a particular method for analysis and location of faults noted on the vehicle by the Customer and/or Service Network personnel.

A correct diagnosis procedure is not merely a set of steps correlated with one another, to be followed automatically in the aim of finding the solution to a specific problem, but rather, a true analysis process intended to single out the causes of the problem.

This analysis process is based on continuous comparison between correct operation and faulty operation of the vehicle and the systems which form it. It is therefore a matter of “proceeding” rationally and logically and not by “trial and error”, to identify the fault and its cause in a univocal manner.

The use of a correct diagnostic method makes it possible to surpass seeking the solution based only on experience and to deal rationally with seeking the cause of the fault.

In an empirical approach to the problem the cause of the fault is either not located or located “by chance” (even if it is “chance” always borne out by the expertise of the technician and his ability).

In a methodologically more correct approach, as suggested here, statistic, i.e. rational, logic is followed, which results in the location and elimination of the cause of the fault the first time the car is taken in by the workshop.

GUIDING PRINCIPLES FOR A CORRECT DIAGNOSIS PROCEDURE

In order to simplify understanding of the diagnosis procedure and its efficacious application, the technician should bear in mind a few basic principles which are the necessary pre-requisites for learning the procedure:

1. Knowing the system

The technician must know how the system works, and its behaviour in the event of a fault. He must also know the peculiarity of the system applied to a specific car and the location of the various components on the car in question. He must also be aware of the structure and contents of the technical literature made available to him.

2. Knowing the history of the car or, of the system and of the fault noted

The technician should inquire if in the past the car has undergone operations that might be put into relation with the fault noted. He should also get to know about the type of operations carried out in particular on the system on which faults occur.

A priority item is to verify whether correct maintenance has been carried out.
He should also find out how the fault arose (e.g. if it occurred suddenly or gradually) and find out the details of “how” the fault occurred: this, in

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